1. Field of the Invention
The present invention relates to a charge capacity parameter estimation system for an electric storage device capable of charging and discharging, which estimates a charge capacity parameter indicative of a charge capacity of the electric storage device.
2. Description of the Related Art
Conventionally, as an estimating device that estimates the capacity of an electric storage device, there has been proposed one disclosed in a Japanese Laid-Open Patent Publication (Kokai) No. H08-339835. The estimating device estimates a remaining capacity as the capacity of the electric storage device, and includes a controller and a current detection circuit that detects electric current flowing from the electric storage device to a load.
In this estimating device, as shown FIG. 4 of Japanese Laid-Open Patent Publication (Kokai) No. H08-339835, when the electric storage device is connected to the controller, a remaining capacity CA is set as an initial value (100%). Then, when a discharging operation of the electric storage device is executed, a dischargeable capacity Ci and an actual discharged capacity CH which is actually discharged in one control period are calculated based on a discharge current I. A percentage CB of the actual discharged capacity CH to the dischargeable capacity Ci is calculated, and then the percentage CB is subtracted from the remaining capacity CA, whereby the remaining capacity CA is calculated, i.e. updated.
According to the above-mentioned estimating device, the remaining capacity CA is calculated by a method of first setting the remaining capacity CA to the initial value (100%), and then, whenever the discharging operation of the electric storage device is executed, subtracting a dropped amount of the remaining capacity caused by the discharging operation. Therefore, when the method is applied to an electric storage device that repeats charging and discharging operations, such as a rechargeable battery, there is a problem that a charged electric quantity cannot be accurately reflected on the remaining capacity CA, so that the remaining capacity CA cannot be accurately calculated.